The name given to a person or employee who's shift pattern requires them to work permanent night shifts. So much so that the person becomes acustomed to being awake all night and asleep all day even on their days off. A common side effect of this condition is insomia at night time and narcolepsy during the day.

I couldnt sleep last night, i was a proper nightshiftboy.

I noticed nightshiftboy didnt wake up till tea time.
What time we leaving the club, 3am? Yeah but i expect nightshiftboy will want to go somewhere else afterward.